1. Field of the Invention
The invention relates in general to a method of producing an added defect count, and more particularly to a method of producing an added defect count by a map to map process.
2. Description of the Related Art
In generally, added defect count is used as an index to monitor the chamber condition of semiconductor apparatus. Only as the defect count is smaller than a certain number, the semiconductor manufacturing is allowed to be processed in the chamber. The defect count also plays as an indication of wafer quality for each manufacturing step, especially for the film deposition step.
Please refer FIG. 1, it shows a flow chart of producing an added defect count for a certain film deposition step according to a traditional method. In step 101, a wafer is scanned before the certain film step is processed and a total particle count P1 is recorded. In step 102, the certain film deposition step, such as depositing a silicon oxide layer, a nitride layer or a metal layer, is manufactured on the wafer. In step 103, the wafer is scanned again after the certain film deposition step is processed and a total particle count P2 is recorded. Finally, in step 104, the added particle is evaluated by subtracting P2 from P1.
However, that some particles appear before the deposition of certain film and disappear after the formation of the certain film usually makes the added defect count as a negative value. Therefore, the added defect count produced from the traditional method not only reflects no real condition of the manufacturing chamber, but also disturbs engineer""s judge.
In the present invention, a method to solve this problem will be disclosed.
The object of the present invention is to provide an added particles to reflect the quality of the wafers or the chambers with more consulting value.
First, a proper pre-dep sensitivity is determined by evaluating common particles and by maximizing the summation of the mapping rate and catching rate. Then, the proper pre-dep sensitivity is applied to the mass-production wafers.
For the process of deciding the proper pre-dep sensitivity, at first, a wafer is scanned with various pre-dep sensitivities, and the pre-dep particle data D1(x,y) is recorded. Second, a film is deposited on the wafer and the wafer is scanned again to record the post-dep particle data D2(x,y) only with a post-dep sensitivity, which is usually the most sensitive scale. Third, the common particle data D3(x,y) is evaluated by comparing the pre-dep particle data D1(x,y) and the post-dep particle data D2(x,y) within an error, ranging from 50 xcexcm to 100 xcexcm. Finally, the proper pre-dep sensitivity is decided by maximizing the summation of a mapping rate and a catching rate, wherein the mapping rate is defined as the ratio of the common particle number D3 to the pre-dep particle number D1, and the catching rate is defined as the ratio of the common particle number D3 to the maximum common particle number D3max.
For the application of the proper pre-dep sensitivity to the mass-production wafers, at first, the mass-production wafers is scanned with the proper pre-dep sensitivity, and the pre-dep particle count P1 is recorded. Second, film deposition, which is same as mentioned before, is processed on the mass-production wafers. Third, the mass-production wafers are scanned again with the most sensitive-scale of the post-dep sensitivities, and the post-dep particle count P2 is recorded. Finally, added particles are calculated by subtracting the post-dep particle count P2 from the pre-dep particle cpunt P1.
Other objects, features, and advantages of the invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings.